1. Field of the Invention
The present invention relates to a heat spreader, a semiconductor package module and a memory module having the heat spreader.
2. Description of the Related Art
According as central processing unit (CPU) speeds have increased, all efforts have been continuously made so as to increase data input/output (I/O) speeds and degrees of integration of main memory, thereby improving the performance of systems including CPUs.
In order to increase the data I/O speeds of the main memory, a bus structure capable of transmitting/receiving packets at high speed has been used between the CPU and the memory. In addition, in order to increase memory capacities of the main memory, memory module has been used. Memory module includes a printed circuit board (PCB) on which a plurality of memory chips is mounted.
A memory module may be classified into a single in-line memory module (SIMM) and a dual in-line memory module (DIMM). The SIMM includes a plurality of semiconductor packages (i.e., memory chips) mounted on only one side of the PCB, and the DIMM has a plurality of the semiconductor packages mounted on both sides of the PCB.
The memory capacities of the main memory may be increased with the use of the memory modules.
Furthermore, a data transmission speed may be increased by using a high clock frequency of the memory in order to provide the advanced data I/O speed of the memory. Additionally, in order to increase the memory capacity, more memory chips may be mounted on the memory module, or the number of slots of a motherboard may be increased so that many memory modules may be mounted on the motherboard.
However, when the clock frequency of the memory is increased, a timing margin of the memory is decreased, and when the number of slots is increased, the transmission of a signal is weakened due to a heavy load on the transmission line. One of a DIMM capable of compensating for the load is referred to as a registered DIMM.
The registered DIMM includes a phase-locked loop (PLL), a register and a plurality of memory chips. The registered DIMM is mounted on the motherboard so as to compensate for the load. However, in case that there are many slots or a high clock frequency, transmission efficiency is decreased due to reflected waves on the transmission line.
In order to improve transmission efficiency, a fully buffered DIMM (FBDIMM) has been provided. The FBDIMM has a hub, such as an advanced memory buffer (AMB) logic chip that is mounted on the center of the memory module.
The AMB receives packet signals including a memory command and/or data from an external host (e.g., a memory controller), and provides the received data to respective memory chips. In addition, the AMB packetizes data outputted from the memory chips, and provide the packets to the memory controller. In the FBDIMM, signals from external sources are transmitted to the respective memory chips via the AMB. Accordingly, all signal lines on which the signals are transmitted are coupled to the AMB. Consequently, a large load is concentrated on the AMB and high heat may be generated in the AMB.
High heat reduces the life span of the AMB (according to the Related Art) and lowers the operational reliability of peripheral circuits of the AMB. Hence, it is advantageous to quickly dissipate away the heat from the AMB.
A conventional FBDIMM includes a heat spreader for radiating the heat of the AMB.
FIG. 1 is a top plan view illustrating an FBDIMM having a conventional heat spreader.
Referring to FIG. 1, an FBDIMM 10 includes a PCB 1, a plurality of semiconductor packages 2 that are mounted on both sides of the PCB 1, an AMB (not shown) that is mounted on one side of the PCB 1, and a heat spreader 3 covering the AMB. The conventional heat spreader 3 has a shape of a thin plate and is fixed on the AMB to form an integral structure.
However, the conventional heat spreader 3 has thermal characteristics that are not sufficient to spread the heat radiated from the AMB.
Furthermore, a process for attaching the heat spreader to the memory module needs is not simple and is not well suited to an automated process for attaching the heat spreader.